RESUMO
Alveolar type 2 (AT2) cells are stem cells of the alveolar epithelia. Previous genetic lineage tracing studies reported multiple cellular origins for AT2 cells after injury. However, conventional lineage tracing based on Cre-loxP has the limitation of non-specific labeling. Here, we introduced a dual recombinase-mediated intersectional genetic lineage tracing approach, enabling precise investigation of AT2 cellular origins during lung homeostasis, injury, and repair. We found AT1 cells, being terminally differentiated, did not contribute to AT2 cells after lung injury and repair. Distinctive yet simultaneous labeling of club cells, bronchioalveolar stem cells (BASCs), and existing AT2 cells revealed the exact contribution of each to AT2 cells post-injury. Mechanistically, Notch signaling inhibition promotes BASCs but impairs club cells' ability to generate AT2 cells during lung repair. This intersectional genetic lineage tracing strategy with enhanced precision allowed us to elucidate the physiological role of various epithelial cell types in alveolar regeneration following injury.
Assuntos
Células Epiteliais Alveolares , Pulmão , Células-Tronco , Animais , Camundongos , Células Epiteliais Alveolares/metabolismo , Células Epiteliais Alveolares/citologia , Diferenciação Celular , Linhagem da Célula , Pulmão/citologia , Pulmão/metabolismo , Pulmão/fisiologia , Lesão Pulmonar/patologia , Camundongos Endogâmicos C57BL , Alvéolos Pulmonares/citologia , Alvéolos Pulmonares/metabolismo , Receptores Notch/metabolismo , Regeneração , Transdução de Sinais , Células-Tronco/metabolismo , Células-Tronco/citologiaRESUMO
The endopeptidase ADAM10 is a critical catalyst for the regulated proteolysis of key drivers of mammalian development, physiology, and non-amyloidogenic cleavage of APP as the primary α-secretase. ADAM10 function requires the formation of a complex with a C8-tetraspanin protein, but how tetraspanin binding enables positioning of the enzyme active site for membrane-proximal cleavage remains unknown. We present here a cryo-EM structure of a vFab-ADAM10-Tspan15 complex, which shows that Tspan15 binding relieves ADAM10 autoinhibition and acts as a molecular measuring stick to position the enzyme active site about 20 Å from the plasma membrane for membrane-proximal substrate cleavage. Cell-based assays of N-cadherin shedding establish that the positioning of the active site by the interface between the ADAM10 catalytic domain and the bound tetraspanin influences selection of the preferred cleavage site. Together, these studies reveal the molecular mechanism underlying ADAM10 proteolysis at membrane-proximal sites and offer a roadmap for its modulation in disease.
Assuntos
Proteína ADAM10 , Animais , Proteína ADAM10/química , Proteína ADAM10/metabolismo , Proteína ADAM10/ultraestrutura , Secretases da Proteína Precursora do Amiloide/química , Mamíferos/metabolismo , Proteólise , Tetraspaninas/metabolismo , HumanosRESUMO
The assembly of the neuronal and other major cell type programs occurred early in animal evolution. We can reconstruct this process by studying non-bilaterians like placozoans. These small disc-shaped animals not only have nine morphologically described cell types and no neurons but also show coordinated behaviors triggered by peptide-secreting cells. We investigated possible neuronal affinities of these peptidergic cells using phylogenetics, chromatin profiling, and comparative single-cell genomics in four placozoans. We found conserved cell type expression programs across placozoans, including populations of transdifferentiating and cycling cells, suggestive of active cell type homeostasis. We also uncovered fourteen peptidergic cell types expressing neuronal-associated components like the pre-synaptic scaffold that derive from progenitor cells with neurogenesis signatures. In contrast, earlier-branching animals like sponges and ctenophores lacked this conserved expression. Our findings indicate that key neuronal developmental and effector gene modules evolved before the advent of cnidarian/bilaterian neurons in the context of paracrine cell signaling.
Assuntos
Evolução Biológica , Invertebrados , Neurônios , Animais , Ctenóforos/genética , Expressão Gênica , Neurônios/fisiologia , Filogenia , Análise de Célula Única , Invertebrados/citologia , Invertebrados/genética , Invertebrados/metabolismo , Comunicação ParácrinaRESUMO
Genetic changes causing brain size expansion in human evolution have remained elusive. Notch signaling is essential for radial glia stem cell proliferation and is a determinant of neuronal number in the mammalian cortex. We find that three paralogs of human-specific NOTCH2NL are highly expressed in radial glia. Functional analysis reveals that different alleles of NOTCH2NL have varying potencies to enhance Notch signaling by interacting directly with NOTCH receptors. Consistent with a role in Notch signaling, NOTCH2NL ectopic expression delays differentiation of neuronal progenitors, while deletion accelerates differentiation into cortical neurons. Furthermore, NOTCH2NL genes provide the breakpoints in 1q21.1 distal deletion/duplication syndrome, where duplications are associated with macrocephaly and autism and deletions with microcephaly and schizophrenia. Thus, the emergence of human-specific NOTCH2NL genes may have contributed to the rapid evolution of the larger human neocortex, accompanied by loss of genomic stability at the 1q21.1 locus and resulting recurrent neurodevelopmental disorders.
Assuntos
Encéfalo/embriologia , Córtex Cerebral/fisiologia , Neurogênese/fisiologia , Receptor Notch2/metabolismo , Transdução de Sinais , Animais , Diferenciação Celular , Células-Tronco Embrionárias/metabolismo , Feminino , Deleção de Genes , Genes Reporter , Gorilla gorilla , Células HEK293 , Humanos , Neocórtex/citologia , Células-Tronco Neurais/metabolismo , Neuroglia/metabolismo , Neurônios/metabolismo , Pan troglodytes , Receptor Notch2/genética , Análise de Sequência de RNARESUMO
Cleavage of membrane-anchored proteins by ADAM (a disintegrin and metalloproteinase) endopeptidases plays a key role in a wide variety of biological signal transduction and protein turnover processes. Among ADAM family members, ADAM10 stands out as particularly important because it is both responsible for regulated proteolysis of Notch receptors and catalyzes the non-amyloidogenic α-secretase cleavage of the Alzheimer's precursor protein (APP). We present here the X-ray crystal structure of the ADAM10 ectodomain, which, together with biochemical and cellular studies, reveals how access to the enzyme active site is regulated. The enzyme adopts an unanticipated architecture in which the C-terminal cysteine-rich domain partially occludes the enzyme active site, preventing unfettered substrate access. Binding of a modulatory antibody to the cysteine-rich domain liberates the catalytic domain from autoinhibition, enhancing enzymatic activity toward a peptide substrate. Together, these studies reveal a mechanism for regulation of ADAM activity and offer a roadmap for its modulation.
Assuntos
Proteína ADAM10/química , Secretases da Proteína Precursora do Amiloide/química , Proteínas de Membrana/química , Proteólise , Proteína ADAM10/metabolismo , Secretases da Proteína Precursora do Amiloide/metabolismo , Cristalografia por Raios X , Humanos , Proteínas de Membrana/metabolismo , Modelos Moleculares , Receptores Notch/metabolismo , Transdução de SinaisRESUMO
DSL ligands activate Notch by inducing proteolytic cleavage of the receptor ectodomain, an event that requires ligand to be endocytosed in signal-sending cells by the adaptor protein Epsin. Two classes of explanation for this unusual requirement are (1) recycling models, in which the ligand must be endocytosed to be modified or repositioned before it binds Notch and (2) pulling models, in which the ligand must be endocytosed after it binds Notch to exert force that exposes an otherwise buried site for cleavage. We demonstrate in vivo that ligands that cannot enter the Epsin pathway nevertheless bind Notch but fail to activate the receptor because they cannot exert sufficient force. This argues against recycling models and in favor of pulling models. Our results also suggest that once ligand binds receptor, activation depends on a competition between Epsin-mediated ligand endocytosis, which induces cleavage, and transendocytosis of the ligand by the receptor, which aborts the incipient signal.
Assuntos
Proteínas de Drosophila/metabolismo , Drosophila/citologia , Drosophila/metabolismo , Endocitose , Transdução de Sinais , Proteínas de Transporte Vesicular/metabolismo , Asas de Animais/metabolismo , Animais , Drosophila/crescimento & desenvolvimento , Discos Imaginais/metabolismo , Ligantes , Receptores Notch/metabolismoRESUMO
Breast cancer is the second leading cause of cancer-related death in women and is a complex disease with high intratumoral and intertumoral heterogeneity. Such heterogeneity is a major driving force behind failure of current therapies and development of resistance. Due to the limitations of conventional therapies and inevitable emergence of acquired drug resistance (chemo and endocrine) as well as radio resistance, it is essential to design novel therapeutic strategies to improve the prognosis for breast cancer patients. Deregulated Notch signaling within the breast tumor and its tumor microenvironment (TME) is linked to poor clinical outcomes in treatment of resistant breast cancer. Notch receptors and ligands are also important for normal mammary development, suggesting the potential for conserved signaling pathways between normal mammary gland development and breast cancer. In this review, we focus on mechanisms by which Notch receptors and ligands contribute to normal mammary gland development and breast tumor progression. We also discuss how complex interactions between cancer cells and the TME may reduce treatment efficacy and ultimately lead to acquired drug or radio resistance. Potential combinatorial approaches aimed at disrupting Notch- and TME-mediated resistance that may aid in achieving in an improved patient prognosis are also highlighted.
Assuntos
Antineoplásicos/uso terapêutico , Neoplasias da Mama/fisiopatologia , Neoplasias da Mama/terapia , Resistencia a Medicamentos Antineoplásicos/genética , Receptores Notch/metabolismo , Transdução de Sinais/fisiologia , Antineoplásicos/farmacologia , HumanosRESUMO
Notch signaling pathway activity, particularly fluctuations in the biologically active effector fragment NICD, is required for rapid and efficient dynamic regulation of proper fate decisions in stem cells. In this study, we identified NEDD4-binding protein 1 (N4BP1), which is highly expressed in the developing mouse cerebral cortex, as a negative modulator of Notch signaling dynamics in neural progenitor cells. Intriguingly, N4BP1 regulated NICD stability specifically after Notch1 S3 cleavage through ubiquitin-mediated degradation that depended on its RAM domain, not its PEST domain, as had been extensively and previously described. The CoCUN domain in N4BP1, particularly the "Phe-Pro" motif (862/863 amino acid), was indispensable for mediating NICD degradation. The Ring family E3 ligase Trim21 was, in contrast to other NEDD4 family members, required for N4BP1-regulated NICD degradation. Overexpression of N4BP1 in cortical neural progenitors promoted neural stem cell differentiation, whereas neural progenitor cells lacking N4BP1 were sensitized to Notch signaling, resulting in the maintenance of stem-like properties in neural progenitor cells and lower production of cortical neurons.
Assuntos
Neocórtex , Células-Tronco Neurais , Animais , Camundongos , Diferenciação Celular/fisiologia , Neocórtex/metabolismo , Células-Tronco Neurais/metabolismo , Neurônios/metabolismo , Receptor Notch1/metabolismo , Receptores Notch/genética , Receptores Notch/metabolismo , Transdução de Sinais/fisiologiaRESUMO
The dorsal aorta (DA) is the first major blood vessel to develop in the embryonic cardiovascular system. Its formation is governed by a coordinated process involving the migration, specification, and arrangement of angioblasts into arterial and venous lineages, a process conserved across species. Although vascular endothelial growth factor a (VEGF-A) is known to drive DA specification and formation, the kinases involved in this process remain ambiguous. Thus, we investigated the role of protein kinase B (Akt) in zebrafish by generating a quadruple mutant (aktΔ/Δ), in which expression and activity of all Akt genes - akt1, -2, -3a and -3b - are strongly decreased. Live imaging of developing aktΔ/Δ DA uncovers early arteriovenous malformations. Single-cell RNA-sequencing analysis of aktΔ/Δ endothelial cells corroborates the impairment of arterial, yet not venous, cell specification. Notably, endothelial specific expression of ligand-independent activation of Notch or constitutively active Akt1 were sufficient to re-establish normal arterial specification in aktΔ/Δ. The Akt loss-of-function mutant unveils that Akt kinase can act upstream of Notch in arterial endothelial cells, and is involved in proper embryonic artery specification. This sheds light on cardiovascular development, revealing a mechanism behind congenital malformations.
Assuntos
Artérias , Proteínas Proto-Oncogênicas c-akt , Receptores Notch , Proteínas de Peixe-Zebra , Peixe-Zebra , Animais , Peixe-Zebra/embriologia , Peixe-Zebra/genética , Peixe-Zebra/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Proteínas Proto-Oncogênicas c-akt/genética , Proteínas de Peixe-Zebra/metabolismo , Proteínas de Peixe-Zebra/genética , Receptores Notch/metabolismo , Receptores Notch/genética , Artérias/embriologia , Artérias/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Células Endoteliais/metabolismo , Transdução de Sinais , Mutação/genética , Embrião não Mamífero/metabolismo , Fator A de Crescimento do Endotélio Vascular/metabolismo , Fator A de Crescimento do Endotélio Vascular/genéticaRESUMO
Adult neural stem cells are mostly quiescent and only rarely enter the cell cycle to self-renew and generate neuronal or glial progenies. The Notch signaling pathway is essential for both the quiescent and proliferative states of neural stem cells. However, these are mutually exclusive cellular states; thus, how Notch promotes both of these programs within adult neural stem cells has remained unclear. In this issue of Genes & Development, Sueda and colleagues (pp. 511-523) use an extensive repertoire of mouse genetic tools and techniques to demonstrate that it is the levels and dynamic expression of the Notch transcriptional effector Hairy and Enhancer of Split 1 that enables this dual role.
Assuntos
Células-Tronco Adultas/citologia , Células-Tronco Neurais/citologia , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Ciclo Celular , Camundongos , Sistema Nervoso , Transdução de Sinais , Fatores de Transcrição HES-1RESUMO
Somatic stem/progenitor cells are active in embryonic tissues but quiescent in many adult tissues. The detailed mechanisms that regulate active versus quiescent stem cell states are largely unknown. In active neural stem cells, Hes1 expression oscillates and drives cyclic expression of the proneural gene Ascl1, which activates cell proliferation. Here, we found that in quiescent neural stem cells in the adult mouse brain, Hes1 levels are oscillatory, although the peaks and troughs are higher than those in active neural stem cells, causing Ascl1 expression to be continuously suppressed. Inactivation of Hes1 and its related genes up-regulates Ascl1 expression and increases neurogenesis. This causes rapid depletion of neural stem cells and premature termination of neurogenesis. Conversely, sustained Hes1 expression represses Ascl1, inhibits neurogenesis, and maintains quiescent neural stem cells. In contrast, induction of Ascl1 oscillations activates neural stem cells and increases neurogenesis in the adult mouse brain. Thus, Ascl1 oscillations, which normally depend on Hes1 oscillations, regulate the active state, while high Hes1 expression and resultant Ascl1 suppression promote quiescence in neural stem cells.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Encéfalo/citologia , Regulação da Expressão Gênica , Células-Tronco Neurais , Neurogênese/genética , Fatores de Transcrição HES-1/genética , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Perfilação da Expressão Gênica , Regulação da Expressão Gênica/genética , Inativação Gênica , Camundongos , Células-Tronco Neurais/citologia , Células-Tronco Neurais/metabolismo , Optogenética , Regiões Promotoras Genéticas , Fatores de Transcrição HES-1/metabolismoRESUMO
Neural proliferation zones mediate brain growth and employ Delta/Notch signaling and HES/Her transcription factors to balance neural stem cell (NSC) maintenance with the generation of progenitors and neurons. We investigated Notch-dependency and function of her genes in the thalamic proliferation zone of zebrafish larvae. Nine Notch-dependent genes, her2, her4.1-4.5, her12, her15.1-15.2, and two Notch-independent genes, her6 and her9, are differentially expressed and define distinct NSC and progenitor populations. her6 prominently executes patterning information to maintain NSCs and the zona limitans intrathalamica Shh signaling activity. Surprisingly, simultaneous deletion of nine Notch-dependent her genes does not affect NSCs or progenitor formation, and her4 overexpression only caused reduction of ascl1b progenitors. Combined genetic manipulations of Notch-dependent and -independent her genes suggest that her6 in the thalamic proliferation zone prominently maintains NSCs and inhibits NSC-to-progenitor lineage transitions. The her gene network is characterized by redundant gene functions, with Notch-independent her genes better substituting for loss of Notch-dependent her genes than vice versa. Together, her gene regulatory feedback loops and cross-regulation contribute to the observed robustness of NSC maintenance.
Assuntos
Proliferação de Células , Regulação da Expressão Gênica no Desenvolvimento , Células-Tronco , Peixe-Zebra , Receptores Notch/genética , Receptores Notch/metabolismo , Células-Tronco Neurais/citologia , Células-Tronco Neurais/metabolismo , Células-Tronco/citologia , Células-Tronco/metabolismo , Encéfalo/citologia , Encéfalo/metabolismo , Família Multigênica , AnimaisRESUMO
Innate and adaptive lymphoid development is orchestrated by the activities of E proteins and their antagonist Id proteins, but how these factors regulate early T cell progenitor (ETP) and innate lymphoid cell (ILC) development remains unclear. Using multiple genetic strategies, we demonstrated that E proteins E2A and HEB acted in synergy in the thymus to establish T cell identity and to suppress the aberrant development of ILCs, including ILC2s and lymphoid-tissue-inducer-like cells. E2A and HEB orchestrated T cell fate and suppressed the ILC transcription signature by activating the expression of genes associated with Notch receptors, T cell receptor (TCR) assembly, and TCR-mediated signaling. E2A and HEB acted in ETPs to establish and maintain a T-cell-lineage-specific enhancer repertoire, including regulatory elements associated with the Notch1, Rag1, and Rag2 loci. On the basis of these and previous observations, we propose that the E-Id protein axis specifies innate and adaptive lymphoid cell fate.
Assuntos
Imunidade Adaptativa , Imunidade Inata , Imunomodulação , Subpopulações de Linfócitos/imunologia , Timócitos/imunologia , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Diferenciação Celular/imunologia , Análise por Conglomerados , Expressão Gênica , Perfilação da Expressão Gênica , Regulação da Expressão Gênica , Redes Reguladoras de Genes , Imunofenotipagem , Proteína 2 Inibidora de Diferenciação/genética , Proteína 2 Inibidora de Diferenciação/metabolismo , Ativação Linfocitária/genética , Ativação Linfocitária/imunologia , Subpopulações de Linfócitos/citologia , Subpopulações de Linfócitos/metabolismo , Células Progenitoras Linfoides/metabolismo , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Fenótipo , Especificidade do Receptor de Antígeno de Linfócitos T/imunologia , Timócitos/citologia , Timócitos/metabolismo , TranscriptomaRESUMO
Notch has been implicated in human cancers and is a putative therapeutic target. However, the regulation of Notch activation in the nucleus remains largely uncharacterized. Therefore, characterizing the detailed mechanisms governing Notch degradation will identify attractive strategies for treating Notch-activated cancers. Here, we report that the long noncoding RNA (lncRNA) BREA2 drives breast cancer metastasis by stabilizing the Notch1 intracellular domain (NICD1). Moreover, we reveal WW domain containing E3 ubiquitin protein ligase 2 (WWP2) as an E3 ligase for NICD1 at K1821 and a suppressor of breast cancer metastasis. Mechanistically, BREA2 impairs WWP2-NICD1 complex formation and in turn stabilizes NICD1, leading to Notch signaling activation and lung metastasis. BREA2 loss sensitizes breast cancer cells to inhibition of Notch signaling and suppresses the growth of breast cancer patient-derived xenograft tumors, highlighting its therapeutic potential in breast cancer. Taken together, these results reveal the lncRNA BREA2 as a putative regulator of Notch signaling and an oncogenic player driving breast cancer metastasis.
Assuntos
Neoplasias da Mama , Neoplasias Pulmonares , RNA Longo não Codificante , Humanos , Feminino , RNA Longo não Codificante/genética , RNA Longo não Codificante/metabolismo , Ubiquitinação , Ubiquitina-Proteína Ligases/genética , Ubiquitina-Proteína Ligases/metabolismo , Neoplasias Pulmonares/genética , Neoplasias da Mama/genética , Receptor Notch1/genética , Receptor Notch1/metabolismoRESUMO
Notch signaling is essential for the emergence of definitive hematopoietic stem cells (HSCs) in the embryo and their development in the fetal liver niche. However, how Notch signaling is activated and which fetal liver cell type provides the ligand for receptor activation in HSCs is unknown. Here we provide evidence that endothelial Jagged1 (Jag1) has a critical early role in fetal liver vascular development but is not required for hematopoietic function during fetal HSC expansion. We demonstrate that Jag1 is expressed in many hematopoietic cells in the fetal liver, including HSCs, and that its expression is lost in adult bone marrow HSCs. Deletion of hematopoietic Jag1 does not affect fetal liver development; however, Jag1-deficient fetal liver HSCs exhibit a significant transplantation defect. Bulk and single-cell transcriptomic analysis of HSCs during peak expansion in the fetal liver indicates that loss of hematopoietic Jag1 leads to the downregulation of critical hematopoietic factors such as GATA2, Mllt3, and HoxA7, but does not perturb Notch receptor expression. Ex vivo activation of Notch signaling in Jag1-deficient fetal HSCs partially rescues the functional defect in a transplant setting. These findings indicate a new fetal-specific niche that is based on juxtracrine hematopoietic Notch signaling and reveal Jag1 as a fetal-specific niche factor essential for HSC function.
Assuntos
Feto , Células-Tronco Hematopoéticas , Adulto , Humanos , Endotélio/metabolismo , Feto/metabolismo , Células-Tronco Hematopoéticas/metabolismo , Fígado/metabolismo , Receptores Notch/genética , Receptores Notch/metabolismoRESUMO
Notch signaling regulates stem cells across animal phylogeny. C. elegans Notch signaling activates transcription of two genes, lst-1 and sygl-1, that encode potent regulators of germline stem cells. The LST-1 protein regulates stem cells in two distinct ways: It promotes self-renewal posttranscriptionally and also restricts self-renewal by a poorly understood mechanism. Its self-renewal promoting activity resides in its N-terminal region, while its self-renewal restricting activity resides in its C-terminal region and requires the Zn finger. Here, we report that LST-1 limits self-renewal by down-regulating Notch-dependent transcription. We detect LST-1 in the nucleus, in addition to its previously known cytoplasmic localization. LST-1 lowers nascent transcript levels at both lst-1 and sygl-1 loci but not at let-858, a Notch-independent locus. LST-1 also lowers levels of two key components of the Notch activation complex, the LAG-1 DNA binding protein and Notch intracellular domain (NICD). Genetically, an LST-1 Zn finger mutant increases Notch signaling strength in both gain- and loss-of-function GLP-1/Notch receptor mutants. Biochemically, LST-1 co-immunoprecipitates with LAG-1 from nematode extracts, suggesting a direct effect. LST-1 is thus a bifunctional regulator that coordinates posttranscriptional and transcriptional mechanisms in a single protein. This LST-1 bifunctionality relies on its bipartite protein architecture and is bolstered by generation of two LST-1 isoforms, one specialized for Notch downregulation. A conserved theme from worms to human is the coupling of PUF-mediated RNA repression together with Notch feedback in the same protein.
Assuntos
Proteínas de Caenorhabditis elegans , Caenorhabditis elegans , Animais , Humanos , Caenorhabditis elegans/genética , Citoplasma , Citosol , Proteínas de Ligação a DNA , Células Germinativas , Receptor do Peptídeo Semelhante ao Glucagon 1 , Proteínas de Caenorhabditis elegans/genéticaRESUMO
The emergence of the sensory organ precursor (SOP) from an equivalence group in Drosophila is a paradigm for studying single-cell fate specification through Notch-mediated lateral inhibition. Yet, it remains unclear how only a single SOP is selected from a relatively large group of cells. We show here that a critical aspect of SOP selection is controlled by cis-inhibition (CI), whereby the Notch ligands, Delta (Dl), cis-inhibit Notch receptors in the same cell. Based on the observation that the mammalian ligand Dl-like 1 cannot cis-inhibit Notch in Drosophila, we probe the role of CI in vivo. We develop a mathematical model for SOP selection where Dl activity is independently regulated by the ubiquitin ligases Neuralized and Mindbomb1. We show theoretically and experimentally that Mindbomb1 induces basal Notch activity, which is suppressed by CI. Our results highlight the trade-off between basal Notch activity and CI as a mechanism for singling out a SOP from a large equivalence group.
Assuntos
Proteínas de Drosophila , Animais , Proteínas de Drosophila/metabolismo , Proteínas de Membrana/fisiologia , Drosophila/metabolismo , Receptores Notch/genética , Transdução de Sinais , Mamíferos/metabolismoRESUMO
Proper organization and orderly mitosis of radial glial progenitors (RGPs) drive the formation of a laminated mammalian cortex in the correct size. However, the molecular underpinnings of the intricate process remain largely unclear. Here we show that RGP behavior and cortical development are controlled by temporally distinct actions of partitioning-defective 3 (PARD3) in concert with dynamic HIPPO signaling. RGPs lacking PARD3 exhibit developmental stage-dependent abnormal switches in division mode, resulting in an initial overproduction of RGPs located largely outside the ventricular zone at the expense of deep-layer neurons. Ectopically localized RGPs subsequently undergo accelerated and excessive neurogenesis, leading to the formation of an enlarged cortex with massive heterotopia and increased seizure susceptibility. Simultaneous removal of HIPPO pathway effectors Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) suppresses cortical enlargement and heterotopia formation. These results define a dynamic regulatory program of mammalian cortical development and highlight a progenitor origin of megalencephaly with ribbon heterotopia and epilepsy.
Assuntos
Moléculas de Adesão Celular/genética , Moléculas de Adesão Celular/metabolismo , Córtex Cerebral/fisiopatologia , Convulsões/genética , Transdução de Sinais , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Animais , Proteínas de Ciclo Celular , Córtex Cerebral/fisiologia , Células Ependimogliais/fisiologia , Deleção de Genes , Regulação da Expressão Gênica no Desenvolvimento , Predisposição Genética para Doença , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Tamanho do Órgão/genética , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , Convulsões/fisiopatologia , Transdução de Sinais/genética , Células-Tronco/fisiologia , Transativadores , Proteínas de Sinalização YAPRESUMO
During mammalian brain development, radial glial progenitors balance between proliferation and differentiation to generate the laminated cortical layers in a temporally precise fashion. Defects in the individual steps going into this complex organogenesis can result in cortical malformations and human nervous system disorders. In this issue of Genes & Development, Liu and colleagues (pp. 763-780) present experimental evidence that an evolutionarily conserved cellular polarity gene, Pard3 (partitioning-defective 3), controls the balance of radial glial proliferation and differentiation through interaction with the Hippo signal transduction pathway. Conditional deletion of Pard3 in the developing rodent cortex resulted in striking subcortical band heterotopia, reminiscent of a severe form of human cortical malformation.
Assuntos
Polaridade Celular , Transdução de Sinais , Proteínas Adaptadoras de Transdução de Sinal , Animais , Proteínas de Ciclo Celular , Diferenciação Celular , Proliferação de Células , Via de Sinalização Hippo , Humanos , Proteínas de Membrana , Neurogênese , Proteínas Serina-Treonina QuinasesRESUMO
Self-renewal genes maintain stem cells in an undifferentiated state by preventing the commitment to differentiate. Robust inactivation of self-renewal gene activity following asymmetric stem cell division allows uncommitted stem cell progeny to exit from an undifferentiated state and initiate the commitment to differentiate. Nonetheless, how self-renewal gene activity at mRNA and protein levels becomes synchronously terminated in uncommitted stem cell progeny is unclear. We demonstrate that a multilayered gene regulation system terminates self-renewal gene activity at all levels in uncommitted stem cell progeny in the fly neural stem cell lineage. We found that the RNA-binding protein Brain tumor (Brat) targets the transcripts of a self-renewal gene, deadpan (dpn), for decay by recruiting the deadenylation machinery to the 3' untranslated region (UTR). Furthermore, we identified a nuclear protein, Insensible, that complements Cullin-mediated proteolysis to robustly inactivate Dpn activity by limiting the level of active Dpn through protein sequestration. The synergy between post-transcriptional and transcriptional control of self-renewal genes drives timely exit from the stem cell state in uncommitted progenitors. Our proposed multilayered gene regulation system could be broadly applicable to the control of exit from stemness in all stem cell lineages.